#include<bits/stdc++.h>
using namespace std;

int main() {
	string s;
	cin >> s;
	map<char, int>mp;
	int ret = 0;
	for(int i = 0; i < s.size(); i ++ ) {
		mp[s[i]] ++ ;
		if(mp[s[i]] == 1) {
			ret ++ ;
		}
	}
	cout << ret << endl;
	return 0;
}
